I think it's just a standard plan now to release at least one expansion pack for every PC-only game, whether it be RPG, RTS, or whatever. Heck, I wouldn't be surprised to learn that the developers actually develop both game and expansion simultaenously and just save the expansion for a later release, followed by a "gold pack OMG!!!" that includes both, and maybe a few more releases further down the road. These days when I see a new strategy game or something that looks interesting, I go "I'd better wait until the inevitable two-pack that includes the expansion. Save some money." Heh. Maybe I'll do the same for Silverfall.